Drain well and transfer potatoes to a mixing bowl or the bowl of your stand mixer.
In a microwave-safe bowl, gently warm together the half & half and butter (about 40 seconds; butter doesn’t have to be fully melted).
Add warmed butter/half & half, room-temp cream cheese, and sour cream to the hot potatoes.
Season with about ½ teaspoon kosher salt, ½ teaspoon onion powder, 1 teaspoon garlic powder (optional), and ¼ teaspoon black pepper.
Beat with a mixer until creamy and smooth. Taste and adjust seasonings as needed. Mary Katherine likes hers extra creamy, so she bumps up the speed for a bit at the end.